1. Field of the Invention
The present invention relates generally to evaporative cooling systems, and more specifically to a mist cooling system for firearms.
2. Description of Related Art
Evaporative cooling systems take advantage of the tremendous amount of energy required to convert a liquid into a gas. This phase change absorbs a lot of energy, thus, the surrounding environment and materials are cooled. This principle has been used in evaporative coolers for dwellings for decades. The evaporative cooler, or swamp cooler, uses water as the coolant medium. The water is passed through and into a medium with a large surface area, such as a foam, sponge or porous filter pad. A fan draws air through the water-laden porous filter pad and some of the water evaporates. The evaporation of water requires a lot of energy and causes the air to be cooled. More recently, misting devices have been used to spray a finely atomized mist of water onto a person to cool the skin and increase comfort as the water mist evaporates. However, such coolers and misting devices are useful only for large areas and external surfaces.
Firearms present a particularly difficult problem. Sustained or prolonged firing makes the barrel too hot to touch. This condition can be aggravated by high ambient temperature conditions, no wind conditions and direct sunshine. High barrel temperatures make a firearm uncomfortable to handle, but other problems can result. Barrel materials, such as steel, expand in response to being heated. This, of course, is normal. However, such heating is rarely linear and evenly distributed. Typically, a barrel will warp or twist as it heats, due to unevenly distributed stresses inherent in the materials during manufacturing. Obviously, a warped or twisted barrel is not conducive to optimal accuracy. Other problems can arise from overheated barrels as well. When a barrel is too hot, a cartridge in the chamber may discharge spontaneously, or cook off. This occurs because the temperature inside the cartridge is high enough to ignite the propellant inside the cartridge. The firearm's lock mechanism is rendered irrelevant. This condition is quite dangerous. Another problem has to do with barrel longevity. Each time a firearm is fired, the hot gasses and plasma from the cartridge's propellant cut and etch the interior of the barrel. This action erodes the precision-machined throat of the barrel, just ahead of the chamber. Unchecked, the barrel erosion process completely destroys a barrel from the inside out. High barrel temperatures can aggravate the erosion process. Thus, temperature control of a firearm barrel is important for sustained accuracy and longevity.
Numerous barrel-cooling devices have been developed over the years. The earliest devices included a water jacket that was attached around machine gun barrels used by our armed forces. This system included a tube over and around virtually the entire barrel. The tube contained water or another liquid coolant and held it in direct contact against the exterior of the barrel. A small reservoir was attached to the jacket via a hose to provide cool water as the water in the jacket heated up. After sustained firing of the firearm, the water could be near boiling. This illustrates how much heat needs to be dissipated, however, the water jacket had some drawbacks. Not only was the water jacket idea heavy, but the hot water could cause burns. Further, the system was potentially fragile and depended upon a watertight jacket that could withstand the rigors of combat use. If no water could be found, or if the supply was exhausted, the jacket trapped heat in the barrel, contrary to the designer's intent.
Another solution was a heat exchanger array. The heat exchanger arrays increased the surface area of the barrel and were attached directly to the barrel to provide addition surface area, in the form of numerous cooling fins. The problem with cooling fins is that they can clog with debris rather easily, like an automotive radiator. The fins could also be very easy to bend or deform. Like the malfunctioning water jacket, a clogged cooling fin array traps heat better than it dissipates heat. The shortcomings of the cooling fin array led to barrel fluting as a solution.
A fluted firearm barrel incorporates a cooling solution directly onto the external surface of the barrel. Grooves, typically longitudinal, are cut into the surface of the barrel to increase the surface area of the barrel. Those grooves are called flutes. However, surface area increases due to fluting are typically very small, unless a large number of very deep cuts are made in the barrel. Any kind of fluting can have drawbacks, however. Like the water jacket and the cooling fins, barrel fluting requires an adequate flow of cooling air to remove the excess heat. In addition, barrel fluting can actually alter the interior dimensions of the barrel as it removes material from the outside of the barrel. As a result, for maximum accuracy, any fluting should be made prior to finishing the bore of the barrel. Thus, it might not be a good idea to add fluting to barrels that are already in use.
None of these devices make it easy to quickly and safely reduce the temperature of a firearm barrel, without requiring complicated, heavy or fragile equipment. Thus, what is needed is a way to quickly, easily and cheaply cool firearm barrels from the inside without altering the barrel or firearm, and without compromising its reliability.